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12 Cards in this Set
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Democritus 5th Century BC |
First theory on atoms Philosophical and ideological reasoning on the existence of atoms Proposed that all matter was made up of tiny indivisible particles known as atomos Atomos differ in size, shape, and arrangement in space. |
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Antoine Laurent Lavoisier 1773 |
Father of modern chemistry Discovered that matter in elements is conserved through his experiments Law of Conservation of mass= Matter is neither created nor destroyed in a chemical reaction. This was the basis for many chemical calculations.
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Joseph Louis Proust |
Law of Definite Proportions: Each compound always contains the same elements in a certain definite proportion and in no other combination |
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John Dalton |
Atomic Theory of Matter: Each element is composed of a unique type of atom which can combine in different ratios to form different compounds. Dalton's Atomic Theory 1. Elements are made of extremely small particles called atoms. 2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. 3. Atoms cannot be subdivided, created, or destroyed. 4. Atoms of different elemente combine in simple whole-number ratios to form chemical compounds. 5. In chemical reactions, atoms are combined. |
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Dmitri Mendeleev 1869 |
Created the periodic table of Elements Arranged Elements (primarily) into ascending order based on atomic mass Grouped together into one column elements with similar chemical properties Discovered previously unknown elements |
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Eugene Goldstein |
Credited with the discovery if a positively charged particle (later to be named the proton) Discovered Anode Rays (Canal Rays) Experimented with gas discharge tubes that had perforated cathodes. |
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Joseph John Thomson |
Discovered and identified the electron through his cathode ray tube experiments. Was able to calculate the charge-to-mass ratio (e/z) of the electron Won 1906 Nobel Prize in Physics Theorized the Plum Pudding Model Atoms have overall neutral charge so there must be a source for both positive and negative charges. Described the Atom as negative particles floating within a sea of diffuse positive charge. |
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Robert Millikan |
Determined the charge of the electron, and consequently, its mass through the oil-drop experiment. 1923 Nobel Prize in Physics. |
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Ernest Rutherford |
Father of nuclear physics Named the positively charged subatomic particle as "proton" Proposed the nuclear atom theory as evidenced by the alpha particle scatterint in his gold foil experiment. Concluded that all positive charge and nearly all the mass of an atom are concentrated at the center of the atom in a tiny core= Nucleus 1908 nobel prize in chemistry |
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Niels Bohr |
Improved Rutherford's model by considering inconsistencies in the classical mechanics. Suggested that the energy of the electron is quantized Quantum= tiny unit in energy 1922 Nobel Prize in physics Energy Level= Specified energy value for an electron. By absorbing quantum energy an electron is promoted to an excited state The electrons return to its ground/relaxed state by releasing a quantum or energy= line spectrum |
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Erwin Schrodinger |
Treated electron as a wave instead of particle. Updated Bohr Model 1933 Nobel Prize in physics Formulated the Schrodinger equation Electrons do not revolve around in an orbit but roam arpund a defines region of 3D space around a nucleus which differs depending on the amount of energy the electron has. |
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James Chadwick |
Discovered the neutron Explained the gain of proton upon beta emission |
